Simple power supply 1.V 2.0AAjout. 2. 01. Subscribe to our VKontakte group - http: //vk. Facebook - https://www. A simple but fairly powerful fixed-voltage power supply can be built using the L7 linear regulator.

SD1. 13, having a maximum collector current of 3. A. A microcircuit stabilizer with the participation of two parallel transistors makes it possible to obtain a stabilized voltage of 1.

V with an output current of 2. A or more, depending on the parameters of the power transformer.

The circuit has short circuit protection. The protection current is determined by the voltage divider in the base of the KT8 transistor. After the protection is triggered or when the power source is turned on, the button must be pressed to put the stabilizer into operating mode. If the protection is triggered, the output voltage will drop to 1. V, and the KT8 transistor will close.

KT8. 16, further, a microcircuit stabilizer and two powerful transistors. The output voltage will drop and will remain in this state for a long time. The power of the power supply depends on the parameters of the power transformer, power filter, and the number of power transistors installed on the corresponding heat sink.

P210 transistors are germanium, powerful low-frequency, p-n-p structures. To power such a radio station from on-board batteries, you need a special power supply that includes a voltage converter.

A simple, but quite powerful power source with the protection current determined by the voltage divider in the base of the KT817 transistor and.

• Voltage stabilizer P210, I want to understand the operating principle. P210 is just a transistor (germanium in my opinion), powerful.
• Diagram of a power supply, power supply, switching. The proposed circuit of a simple (only 3 transistors) power supply is advantageous.
• If there is a short circuit at the output of the power supply, the emitter of transistor VT1 will be connected to the anode of the diode VD5, and to it.
• Replacing transistors in a laboratory power supply. Charger based on PC power supplies. BP is free from it.
• P210 transistors are germanium, powerful low-frequency, p-n-p structures.
• A charger based on a p210 transistor can be repaired without much effort. Diagram of a power supply with a p210 transistor.

The power supply circuit with a stabilizer based on the P210 transistor is shown in Figure 1. At one time this was a very popular circuit. It could be found in various modifications, both in industrial equipment and in amateur radio equipment.

The entire circuit is assembled in a hinged manner directly on the radiator, using support stands and rigid transistor terminals. The radiator area at a load current of six amperes should be about 500 cm². Since the collectors of transistors VT1 and VT2 are connected, there is no need to isolate their cases from each other, but it is better to isolate the radiator itself from the case (if it is metal). Diodes D1 and D2 - any 10A. The area of ​​radiators for diodes is ≈ 80 cm². You can roughly calculate the heat sink area for different semiconductor devices, so to speak, using the diagram given in the article. I usually use U-shaped radiators, bent from a strip of three-millimeter aluminum (see photo 1).
Strip size 120x35mm. Transformer Tr1 is a rewound transformer from a TV. For example, TS-180 or similar. The diameter of the secondary winding wire is 1.25 ÷ 1.5 mm. The number of turns of the secondary winding will depend on the transformer you use. How to calculate a transformer can be found in the article, section - “Independent calculations”. Each of windings III and IV must be designed for a voltage of 16V. By replacing the tuning resistor R4 with a variable one and adding an ammeter to the circuit, you can charge car batteries with this power supply.

Typical mistakes when designing germanium amplifiers occur due to the desire to get a wide bandwidth, low distortion, etc. from the amplifier.
Here is a diagram of my first germanium amplifier, designed by me in 2000.
Although the circuit is quite functional, its sound qualities leave much to be desired.

Practice has shown that the use of differential cascades, current generators, cascades with dynamic loads, current mirrors and other tricks with environmental feedback do not always lead to the desired result, and sometimes simply lead to a dead end.
The best practical results for obtaining high sound quality are obtained by using single-ended cascades. amplification and the use of inter-stage matching transformers.
We present to your attention a germanium amplifier with an output power of 60 W, into a load of 8 ohms. Output transistors used in the amplifier are P210A, P210Sh. Linearity 20-16000Hz.
There is practically no subjective lack of high frequencies.
With a 4-ohm load, the amplifier produces 100 watts.

Amplifier circuit using P-210 transistors.

The amplifier is powered by an unstabilized power supply with a bipolar output voltage of +40 and -40 volts.
For each channel, a separate bridge of D305 diodes is used, which are installed on small radiators.
Filter capacitors, it is advisable to use at least 10,000 microns per arm.
Power transformer data:
-iron 40 to 80. The primary winding contains 410 vit. wires 0.68. Secondary at 59 vit. 1.25 wires, wound four times (two windings - the upper and lower arms of one amplifier channel, the remaining two - the second channel)
.Additionally regarding the power transformer:
iron w 40 by 80 from the power supply of the KVN TV. After the primary winding, a copper foil screen is installed. One open turn. A lead is soldered to it which is then grounded.
You can use any iron that has a suitable cross-section.
The matching transformer is made of Sh20 by 40 iron.
The primary winding is divided into two parts and contains 480 vit.
The secondary winding contains 72 turns and is wound in two wires simultaneously.
First, 240 vit of the primary is wound, then the secondary, then again 240 vit of the primary.
The diameter of the primary wire is 0.355 mm, the secondary is 0.63 mm.
The transformer is assembled into a joint, the gap is a cable paper gasket of approximately 0.25 mm.
A 120 Ohm resistor is included to ensure no self-excitation when the load is off.
Chains 250 Ohm +2 x 4.7 Ohm are used to supply the initial bias to the bases of the output transistors.
Using 4.7 Ohm trimmers, the quiescent current is set to 100mA. The resistors in the emitters of the output transistors are 0.47 Ohms, and there should be a voltage of 47 mV.
The output transistors P210 should be almost barely warm.
To accurately set the zero potential, 250 Ohm resistors must be precisely selected (in a real design they consist of four 1 kOhm 2W resistors).
To smoothly set the quiescent current, trimming resistors R18, R19 type SP5-3V 4.7 Ohm 5% are used.
The rear view of the amplifier is shown in the photo below.

May I know your impressions of the sound of this version of the amplifier, in comparison with the previous transformerless version on the P213-217?

Even more rich, juicy sound. I would especially like to emphasize the quality of the bass. The listening was carried out with open acoustics on 2A12 speakers.

- Jean, why exactly are P215 and P210, and not GT806/813, included in the diagram?

Carefully look at the parameters and characteristics of all these transistors, I think you will understand everything, and the question will disappear by itself.
I am clearly aware of the desire of many to make the germanium amplifier more broadband. But the reality is that many high-frequency germanium transistors are not entirely suitable for audio purposes. Of the domestic ones, I can recommend P201, P202, P203, P4, 1T403, GT402, GT404, GT703, GT705, P213-P217, P208, P210. The method of expanding the bandwidth is the use of circuits with a common base, or the use of imported transistors.
The use of circuits with transformers has made it possible to achieve excellent results on silicon. An amplifier based on 2N3055 has been developed.
I'll share it soon.

- What about the “0” at the output? With a current of 100 mA, it is hard to believe that it will be possible to keep it at an acceptable +-0.1 V during operation.
In similar circuits from 30 years ago (Grigoriev’s circuit), this is solved either by a “virtual” midpoint or by an electrolyte:

Grigoriev amplifier.

The zero potential is maintained within the limit you specify. The quiescent current can be set to 50mA. Monitored with an oscilloscope until the step disappears. No more need. Further, all op-amps can easily handle a 2k load. Therefore, there are no special coordination problems with CD.
Some high-frequency germanium transistors require attention and additional study in audio circuits. 1T901A, 1T906A, 1T905A, P605-P608, 1TS609, 1T321. Try it and gain experience.
Sometimes sudden failures of transistors 1T806, 1T813 occurred, so I can recommend them with caution.
They need to install “fast” current protection, designed for a current greater than the maximum in a given circuit. To prevent protection from triggering in normal mode. Then they work very reliably.
I’ll add my version of Grigoriev’s scheme

Version of Grigoriev's amplifier circuit.

By selecting a resistor from the base of the input transistor, half the supply voltage is set at the point where the 10 ohm resistors connect. By selecting a resistor in parallel with the 1N4148 diode, the quiescent current is set.

- 1. In my reference books, D305 is normalized to 50V. Is it safer to use D304? I think 5A is enough.
- 2. Indicate real h21 for devices installed in this layout or their minimum required values.

You are absolutely right. If there is no need for high power. The voltage across each diode is about 30V, so there are no reliability issues. Transistors with the following parameters were used; P210 h21-40, P215 h21-100, GT402G h21-200.

The stabilized power supply discussed below is one of the first devices that are assembled by novice radio amateurs. This is a very simple but very useful device. Its assembly does not require expensive components, which are quite easy for a beginner to select depending on the required characteristics of the power supply.
The material will also be useful to those who want to understand in more detail the purpose and calculation of simple radio components. Including, you will learn in detail about such components of the power supply as:

• power transformer;
• diode bridge;
• smoothing capacitor;
• Zener diode;
• resistor for zener diode;
• transistor;
• load resistor;
• LED and resistor for it.

The article also describes in detail how to select radio components for your power supply and what to do if you do not have the required rating. The development of a printed circuit board will be clearly shown and the nuances of this operation will be revealed. A few words are said specifically about checking radio components before soldering, as well as about assembling the device and testing it.

Typical circuit of a stabilized power supply

There are a lot of different power supply circuits with voltage stabilization today. But one of the simplest configurations, which a beginner should start with, is built on just two key components - a zener diode and a powerful transistor. Naturally, there are other details in the diagram, but they are auxiliary.

Circuits in radio electronics are usually disassembled in the direction in which current flows through them. In a voltage-regulated power supply, it all starts with the transformer (TR1). It performs several functions at once. Firstly, the transformer reduces the mains voltage. Secondly, it ensures the operation of the circuit. Thirdly, it powers the device that is connected to the unit.
Diode bridge (BR1) – designed to rectify low mains voltage. In other words, an alternating voltage enters it, and the output is constant. Without a diode bridge, neither the power supply itself nor the devices that will be connected to it will work.
A smoothing electrolytic capacitor (C1) is needed in order to remove ripples present in the household network. In practice, they create interference that negatively affects the operation of electrical appliances. If, for example, we take an audio amplifier powered from a power supply without a smoothing capacitor, then these same pulsations will be clearly audible in the speakers in the form of extraneous noise. In other devices, interference can lead to incorrect operation, malfunctions and other problems.
The Zener diode (D1) is a component of the power supply that stabilizes the voltage level. The fact is that the transformer will produce the desired 12 V (for example) only when there is exactly 230 V in the power outlet. However, in practice such conditions do not exist. The voltage can either drop or rise. The transformer will produce the same at the output. Thanks to its properties, the zener diode equalizes the low voltage regardless of surges in the network. For correct operation of this component, a current-limiting resistor (R1) is required. It is discussed in more detail below.
Transistor (Q1) – needed to amplify the current. The fact is that the zener diode is not capable of passing through itself all the current consumed by the device. Moreover, it will work correctly only in a certain range, for example, from 5 to 20 mA. This is frankly not enough to power any devices. This problem is solved by a powerful transistor, the opening and closing of which is controlled by a zener diode.
Smoothing capacitor (C2) - designed for the same thing as C1 described above. In typical circuits of stabilized power supplies there is also a load resistor (R2). It is needed so that the circuit remains operational when nothing is connected to the output terminals.
Other components may be present in such circuits. This is a fuse that is placed in front of the transformer, and an LED that signals that the unit is turned on, and additional smoothing capacitors, and another amplifying transistor, and a switch. All of them complicate the circuit, however, they increase the functionality of the device.

Calculation and selection of radio components for a simple power supply

The transformer is selected according to two main criteria - secondary winding voltage and power. There are other parameters, but within the framework of the material they are not particularly important. If you need a power supply, say, 12 V, then the transformer needs to be selected so that a little more can be removed from its secondary winding. With power, everything is the same - we take it with a small margin.
The main parameter of a diode bridge is the maximum current that it can pass. This characteristic is worth focusing on first. Let's look at examples. The block will be used to power a device that consumes a current of 1 A. This means that the diode bridge needs to be taken at approximately 1.5 A. Let's say you plan to power a 12-volt device with a power of 30 W. This means that the current consumption will be about 2.5 A. Accordingly, the diode bridge must be at least 3 A. Its other characteristics (maximum voltage, etc.) can be neglected within the framework of such a simple circuit.

Additionally, it is worth saying that you don’t have to take a ready-made diode bridge, but assemble it from four diodes. In this case, each of them must be designed for the current passing through the circuit.
To calculate the capacity of the smoothing capacitor, rather complex formulas are used, which in this case are of no use. Usually a capacitance of 1000-2200 uF is taken, and this will be quite enough for a simple power supply. You can take a larger capacitor, but this will significantly increase the cost of the product. Another important parameter is the maximum voltage. According to it, the capacitor is selected depending on what voltage will be present in the circuit.
Here it is worth considering that in the segment between the diode bridge and the zener diode, after turning on the smoothing capacitor, the voltage will be approximately 30% higher than at the transformer terminals. That is, if you are making a 12 V power supply, and the transformer produces 15 V with a reserve, then in this section due to the operation of the smoothing capacitor there will be approximately 19.5 V. Accordingly, it must be designed for this voltage (the closest standard value 25 V).
The second smoothing capacitor in the circuit (C2) is usually taken with a small capacitance - from 100 to 470 μF. The voltage in this section of the circuit will already be stabilized, for example, to a level of 12 V. Accordingly, the capacitor must be designed for this (the nearest standard rating is 16 V).
But what to do if capacitors of the required ratings are not available, and you don’t want to go to the store (or simply don’t want to buy them)? In this case, it is quite possible to use parallel connection of several capacitors of smaller capacity. It is worth considering that the maximum operating voltage with such a connection will not be summed up!
The zener diode is selected depending on what voltage we need to get at the output of the power supply. If there is no suitable value, then you can connect several pieces in series. The stabilized voltage will be summed up. For example, let's take a situation where we need to get 12 V, but there are only two 6 V zener diodes available. By connecting them in series we will get the desired voltage. It is worth noting that to obtain the average rating, connecting two zener diodes in parallel will not work.
It is possible to select the current-limiting resistor for a zener diode as accurately as possible only experimentally. To do this, a resistor with a nominal value of approximately 1 kOhm is connected to an already working circuit (for example, on a breadboard), and an ammeter and a variable resistor are placed between it and the zener diode in the open circuit. After turning on the circuit, you need to rotate the variable resistor knob until the required rated stabilization current flows through the circuit section (indicated in the characteristics of the zener diode).
The amplifying transistor is selected according to two main criteria. Firstly, for the circuit under consideration it must be an n-p-n structure. Secondly, in the characteristics of the existing transistor you need to look at the maximum collector current. It should be slightly greater than the maximum current for which the assembled power supply will be designed.
The load resistor in typical circuits is taken with a nominal value from 1 kOhm to 10 kOhm. You should not take a smaller resistance, since if the power supply is not loaded, too much current will flow through this resistor and it will burn out.

PCB design and manufacturing

Now let’s briefly look at a clear example of developing and assembling a stabilized power supply with your own hands. First of all, you need to find all the components present in the circuit. If there are no capacitors, resistors or zener diodes of the required ratings, we get out of the situation using the methods described above.

Next, we will need to design and manufacture a printed circuit board for our device. For beginners, it is best to use simple and, most importantly, free software, such as Sprint Layout.
We place all components on the virtual board according to the selected circuit. We optimize their location and adjust them depending on what specific parts are available. At this stage, it is recommended to double-check the actual dimensions of the components and compare them with those added to the developed circuit. Pay special attention to the polarity of electrolytic capacitors, the location of the terminals of the transistor, zener diode and diode bridge.
If you want to add a signal LED to the power supply, then it can be included in the circuit both before the zener diode and after (preferably). To select a current-limiting resistor for it, you need to perform the following calculation. From the voltage of the circuit section, we subtract the voltage drop across the LED and divide the result by the rated current of its supply. Example. In the area to which we plan to connect the signal LED, there is a stabilized 12 V. The voltage drop for standard LEDs is about 3 V, and the rated supply current is 20 mA (0.02 A). We find that the resistance of the current-limiting resistor is R = 450 Ohms.

Checking components and assembling the power supply

After developing the board in the program, we transfer it to fiberglass laminate, etch it, tin the tracks and remove excess flux.
Resistors are checked with an ohmmeter. The zener diode should only “ring” in one direction. We check the diode bridge according to the diagram. The diodes built into it must conduct current in only one direction. To test capacitors you will need a special device for measuring electrical capacitance. In an n-p-n transistor, current must flow from the base to the emitter to the collector. It should not flow in other directions.
It is best to start assembly with small parts - resistors, zener diode, LED. Then the capacitors and diode bridge are soldered in.
Pay special attention to the process of installing a powerful transistor. If you confuse its conclusions, the circuit will not work. In addition, this component will get quite hot under load, so it must be installed on a radiator.
The largest part is installed last - the transformer. Next, a power plug with a wire is soldered to the terminals of its primary winding. Wires are also provided at the output of the power supply.

All that remains is to thoroughly double-check the correct installation of all components, wash off the remaining flux and turn on the power supply to the network. If everything is done correctly, the LED will light up, and the multimeter will show the desired voltage at the output.

The proposed power supply is made of transistors. It has a relatively simple circuit (Fig. 1), and the following parameters:

output voltage................................................ .................................... 3...30 V;
stabilization coefficient when the network voltage changes from 200 to 240 V......... 500;
maximum load current........................................................ .................................... 2 A;
temperature instability................................................... ........................... 10 mV/°C;
pulsation amplitude at I max................................................... ............................... 2 mV;
output impedance........................................................ ................................ 0.05 Ohm.

The main rectifier is assembled using diodes VD5-VD8, the voltage from which is supplied to the filter capacitor C2 and the regulating composite transistor VT2, VT4-VT6, connected according to a common collector circuit.
A feedback signal amplifier is made on transistors VT3, VT7. Transistor VT7 is powered by the output voltage of the power supply. Resistor R9 is its load. The emitter voltage of transistor VT7 is stabilized by a zener diode VD17. As a result, the current of this transistor depends only on the base voltage, which can be changed by changing the voltage drop across resistor R10 of the voltage divider R10, R12-R21. Any increase or decrease in the base current of transistor VT7 leads to an increase or decrease in the collector current of transistor VT3. In this case, the regulating element is locked or unlocked to a greater extent, correspondingly reducing or increasing the output voltage of the power supply. By commutating resistors R13-R21 with section SA2.2 of switch SA2, the output voltage of the unit is changed in steps of 3 V. Smoothly within each step, the output voltage is adjusted using resistor R12.

An auxiliary parametric stabilizer on the zener diode VD9 and resistor R1 serves to power the transistor VT3, the supply voltage of which is equal to the sum of the output voltage of the unit and the stabilization voltage of the zener diode VD9. Resistor R3 is the load of transistor VT3.

Capacitor C4 eliminates self-excitation at high frequencies, capacitor C5 reduces output voltage ripple. Diodes VD16, VD15 accelerate the discharge of capacitor C6 and the capacitive load connected to the block when setting a lower output voltage level.

Transistor VT1, thyristor VS1 and relay K1 are used to protect the power supply from overload. As soon as the voltage drop across resistor R5, proportional to the load current, exceeds the voltage across diode VD12, transistor VT1 opens. Following it, the thyristor VS1 opens, shunting the base of the regulating transistor through the diode VD14, and the current through the regulating element of the stabilizer is limited. At the same time, relay K1 is activated, contacts K1.2 connecting the base of the control transistor with the common wire. Now the output current of the stabilizer is determined only by the leakage current of transistors VT2, VT4-VT6. With contacts K1.1, relay K1 turns on the lamp H2 “Overload”. To return the stabilizer to its original mode, you need to turn it off for a few seconds and turn it on again. To eliminate the voltage surge at the output of the unit when it is turned on, as well as to prevent the protection from tripping under a significant capacitive load, capacitor C3, resistor R2 and diode VD11 are used. When the power supply is turned on, the capacitor is charged in two circuits: through resistor R2 and through resistor R3 and diode VD11. In this case, the voltage at the base of the control transistor slowly increases following the voltage at capacitor C3 until the stabilization voltage is established. Then diode VD11 closes and capacitor C3 continues to charge through resistor R2. Diode VD11, when closing, eliminates the influence of the capacitor on the operation of the stabilizer. Diode VD10 serves to accelerate the discharge of capacitor C3 when the power supply is turned off.

All elements of the power supplies, except for the power transformer, powerful control transistors, switches SA1-SA3, fuse holders FU1, FU2, light bulbs H1, H2, dial meter, output connectors and stepless output voltage regulator, are placed on printed circuit boards.

The location of the power supply units inside the case can be seen in Fig. 4. P210A transistors are mounted on a needle-shaped radiator installed at the rear of the case and having an effective dissipation area of ​​​​about 600 cm 2. Ventilation holes with a diameter of 8 mm are drilled in the bottom of the case where the radiator is attached. The housing cover is secured in such a way that an air gap of about 0.5 cm wide is maintained between it and the radiator. For better cooling of the control transistors, it is recommended to drill ventilation holes in the cover.

A power transformer is fixed in the center of the case, and next to it, on the right side, a P214A transistor is fixed on a duralumin plate measuring 5x2.5 cm. The plate is insulated from the body using insulating sleeves. The KD202V diodes of the main rectifier are installed on duralumin plates screwed to the printed circuit board. The board is installed above the power transformer with the parts facing down.

The power transformer is made on a toroidal tape magnetic core OL 50-80/50. The primary winding contains 960 turns of PEV-2 0.51 wire. Windings II and IV have output voltages of 32 and 6 V, respectively, with a voltage on the primary winding of 220 V. They contain 140 and 27 turns of PEV-2 0.31 wire. Winding III is wound with PEV-2 1.2 wire and contains 10 sections: the bottom (according to the diagram) - 60, and the rest - 11 turns. The output voltages of the sections are respectively 14 and 2.5 V. The power transformer can also be wound on another magnetic circuit, for example on the rod from CNT 47/59 TVs and others. The primary winding of such a transformer is retained, and the secondary windings are rewound to obtain the above voltages.

In power supplies, instead of P210A transistors, you can use transistors of the P216, P217, P4, GT806 series. Instead of transistors P214A, any of the P213-P215 series. MP26B transistors can be replaced with any of the MP25, MP26 series, and P307V transistors with any of the P307 - P309, KT605 series. D223A diodes can be replaced with D223B, KD103A, KD105 diodes; KD202V diodes - any powerful diodes with a permissible current of at least 2 A. Instead of the D818A zener diode, you can use any other zener diode from this series. Instead of the KU101B thyristor, any of the KU101, KU102 series will do. As relay K1, a small-sized relay of type RES-9 was used, passports: RS4.524.200, RS4.524.201, RS4.524.209, RS4.524.213.

The relays of the specified passports are designed for an operating voltage of 24...27 V, but begin to operate already at a voltage of 15...16 V. If an overload of the power supply occurs (see Fig. 2), as already noted, the thyristor VS1 is unlocked, which limits stabilizer current to a small value. In this case, the filter capacitor of the main rectifier (C2) is immediately recharged to approximately the amplitude value of the alternating voltage (with the switch SA2.1 in the lower position, this voltage is at least 20 V) and conditions are created for fast and reliable operation of the relay.

SA2 switches are small-sized biscuits of type 11P3NPM. In the second block, the contacts of two sections of this switch are paralleled and are used to switch sections of the power transformer. When the power supply is turned on, the position of switch SA2 should be changed at load currents not exceeding 0.2...0.3 A. If the load current exceeds the specified values, then to prevent sparking and burning of the switch contacts, change the output voltage of the unit only after turning it off. Variable resistors for smooth adjustment of the output voltage should be selected with resistance depending on the angle of rotation of the “A” type engine and preferably wire resistors. Miniature incandescent light bulbs NSM-9 V-60 mA were used as signal lights H1, H2.

Any pointer device can be used with a total pointer deflection current of up to 1 mA and a face size of no more than 60X60 mm. It must be remembered that including a shunt in the output circuit of the power supply increases its output resistance. The greater the current of the total deflection of the device needle, the greater the shunt resistance (provided that the internal resistances of the devices are of the same order). To prevent the device from influencing the output resistance of the power supply, switch SA3 during operation should be set to voltage measurement (the top position in the diagram). In this case, the device shunt is closed and excluded from the output circuit.

The setup comes down to checking the correct installation, selecting resistors of the control stages to adjust the output voltage within the required limits, setting the protection response current and selecting the resistances of the resistors Rsh and Rd for the dial meter. Before setting up, instead of a shunt, solder a short wire jumper.

When setting up the power supply, switch SA2 and resistor R12 are set to the position corresponding to the minimum output voltage (lowest position in the diagram). By selecting resistor R21, we achieve a voltage of 2.7...3 V at the output of the block. Then move the slider of resistor R12 to the extreme right position (upper in the diagram) and by selecting resistor R10 set the voltage at the output of the block equal to 6 - 6.5 V. Next move switch SA2 one position to the right and select resistor R20 so that the output voltage of the unit increases by 3 V. And so in order, each time moving switch SA2 one position to the right, select resistors R19-R13 until the final voltage is established at the output of the power supply 30 V. Resistor R12 for smooth adjustment of the output voltage can be taken with a different value: from 300 to 680 Ohms, however, the resistance of resistors R10, R13-R20 needs to be changed approximately proportionally.

The protection operation is adjusted by selecting resistor R5.

The additional resistor Rd and shunt Rsh are selected by comparing the readings of the PA1 meter with the readings of an external measuring device. In this case, the external device must be as accurate as possible. As an additional resistor, you can use one or two OMLT, MT resistors connected in series with a dissipation power of at least 0.5 W. When selecting a resistor Rd, switch SA3 is switched to the “Voltage” position and the voltage at the output of the power supply is set to 30 V. An external device, not forgetting to switch it to voltage measurement, is connected to the output of the unit.